Perhaps you should try some spelling variations:
hieu quan » lieu quan, thien quan, lien quan
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
doi cua » dai cua, hoi cua
nam tu » nam thu, nam thuc
tu van » tu va
di cua » dai cua, de cua, do cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh ((di cua) OR (doi cua)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang x ho. ((hieu quan) OR (hieu qua)) nam tu van hanh ((di cua) OR (doi cua)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh ((di cua) OR (doi cua)) tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. ((hieu quan) or (hieu qua)) nam tu van hanh ((di cua) OR (doi cua)) tre*.